I would suggest you make an appointment with your internist to have an examination. A sharp pain that has lasted two weeks can implicate a number of possible problems - some of them serious and some easily treated.
It is possible that you have (unknowingly) injured a muscle in the chest or between the ribs (called the intercostal muscles). Muscle injuries can be tender, be painful (including sharp pain), and are often difficult to heal on their own especially in certain areas of the body like the chest. This is because every time you breath the chest moves, and an injured muscle may never get a chance to rest enough to heal.
A sharp pain over a 2-week period can also indicate an aneurysm of a major blood vessel in the chest. While this is not very likely in a young woman, it does happen at every age and can require rapid surgical repair.
With such a wide range of possibilities I strongly suggest you call your doctor and explain that need to be seen today or tomorrow.
If you experience any of the following symptoms I would call 911 or go the emergency room right away: dizziness/light-headedness, pain that extends into the jaw, neck, or upper back or the pain feels different (such as a tearing pain or sharp pain that isn't going away), shortness of breath/wheezing/severe coughing, or drop in blood pressure/paling (whitening) of the skin color.
While an aneurysm is not likely, it needs to be ruled out as soon as possible, so try to get in to see your doctor today if possible.